1. Field of the Invention
The present invention relates to an exhaust treatment apparatus, such as a catalytic converter or the like, having a low restriction end tube useful for reducing back pressure in the exhaust system of an internal combustion engine.
2. Description of the Relevant Art
Typical automotive vehicle exhaust systems incorporate a catalytic converter and at least one muffler or other noise attenuator. Many of these devices have similar external housings which have conical or truncated end portions, see FIG. 5, that necessitate the insertion of end tubes 28a and 30a through apertures formed therein. The end tubes allow the devices to be easily assembled to the exhaust system of an automobile by axial sliding engagement therewith.
In order to facilitate the insertion of the end tubes into the end portions of the converters or mufflers, the tubes 28a often have a taper 36a, see FIG. 4, at the insertion end thereof. The taper 36a reduces the end diameter of the tube to provide a lead-in radius for guiding the tubes into the end portion of the device 10a. While the tapered end tubes 28a and 30a greatly simplify assembly, the end result is a marked increase in overall exhaust system back pressure. The taper increases the severity of flow separation at the inlet to the shell and in the outlet tube itself, as shown in FIG. 5, leading to a reduction in exhaust system efficiency. Such increases in system back pressure are undesirable from the standpoint of system efficiency.